Riverbed transformation as a result of a ferry crossing construction – case study

Abstract

Riverbed under the influence of natural and anthropogenic factors is constantly being transformed. The changes of the channel parameters related to natural phenomena are rarely dynamic. Contrarily it is in the case of human activity. The introduction of river engineering structures to the riverbed aims to quickly adapt the river to the requirements. If construction of such forms is designed taking account of natural conditions prevailing in the riverbed, then negative effects cannot be observed. The situation is different when the river's characteristics were not considered in the design process. The article discusses the changes that the riverbed has undergone due to its intensive contraction at the ferry crossing at km 488 of Vistula, in Gassy. Current and archival aerial photographs were analyzed in terms of the transformation of the riverbed width, as well as the size of the mid-channel islands. The focus was concentrated on a section of the river 2 km above and 4 km below the ferry crossing. In particular, the parameters of the channel bar located directly below the narrowing and their change over the last decades were analyzed. Conclusions were drawn regarding the case study and recommendations for designing analogous solutions ensuing from the analysis were formulated.

Dynamics of mid-channel bars in the Middle Vistula River in response to ferry crossing abutment construction

“…There is only one exception, on the right bank along the bow downstream the crossing, the process of bank erosion was observed. As it was stated in [18], the right bank of the channel has moved around 270 m (from 1959 to 2003). In the second localization (Brzumin), slight changes in shorelines along the section are visible as well.…”

The concept for innovative Comprehensive Assessment of Lowland Rivers

“…For example, it was shown that the channel's narrowing due to the construction of a ferry crossing caused intensive sedimentation downstream of the narrowing in the expansion zone. In contrast, bank erosion and the channel bar strengthening outwash were observed under other flow conditions [59]. The analyses indicate that hydropower plants can also influence the river's hydromorphological conditions, although their impact is ambiguous.…”

“…The final index values are then calculated using specific formulas. The score obtained from the calculation (0-100) is compared to the five-point NSFWQI rating scale excellent (91-100), good (71)(72)(73)(74)(75)(76)(77)(78)(79)(80)(81)(82)(83)(84)(85)(86)(87)(88)(89)(90), moderate (51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)(70), low and bad (0-25), [93,94]. Another index commonly used in river assessment is the Water Pollution Index (WPI).…”